Operators of cable television systems, also known as Multiple Service Operators (MSOs), continuously make attempts to offer faster service to meet customer demand and competition for better service, yielding higher peak rates year after year. Data Over Cable Service Interface Specification (DOCSIS) is a cable communication standard developed to permit the addition of high-bandwidth data transfers to an existing cable television (CATV) system. It is employed internationally by many cable television operators to provide internet access over existing infrastructures, such as a hybrid fiber-coaxial (HFC) infrastructure, for example.
Upstream (US) resource allocation and scheduling in DOCSIS networks continue to have challenges that are different from those of downstream (DS) scheduling, where the traffic is broadcasted to all modems at once. Issues in the US direction that affect network migration include noise funneling, distortion, burst transmission, topology resolution, multiple access, etc.
To accommodate higher peak rates, the Data Over Cable Service Interface Specification (DOCSIS) 3.1 specifications were developed and issued in 2013. The DOCSIS 3.1 standard promises a great capacity potential by extending the spectrum in both the downstream (DS) and upstream (US) directions. DOCSIS 3.1 extends the spectrum by using, in part, a modern PHY technology (i.e., Orthogonal Frequency Division Multiplexing (OFDM)), and improved Forward Error Correction (FEC) technology (i.e., Low Density Parity Check Codes (LDPC)).
The migration to DOCSIS 3.1 may be challenging due to differences in technology from DOCSIS 3.0 to DOCSIS 3.1. For example, the migration in the US can be more challenging than the DS due to the limited available spectrum and the potential spectral overlap for DOCSIS 3.1 OFDMA channels and DOCSIS 3.0 Single-Carrier Quadrature Amplitude Modulation (SC-QAM) channels. Further, the DOCSIS 3.1 specification defines parameters that are not always efficient to implement. DOCSIS 3.1 requires the use of 192 MHz wide downstream OFDM signal, created by an inverse fast Fourier transform (IFFT) procedure and based on a clock frequency 204.8 MHz. In implementations, these parameters may conflict with design constraints of cable modem termination systems (CMTSs). In another example, the DOCSIS 3.1 standard defines a particular clock frequency which may conflict with clock frequencies that already exist or may be inconvenient to use in a current design. Since OFDM devices are not functioning in isolation, and may require a different clock frequency, a specific frequency could create problematic design changes. In some cases, limits on changing hardware prevents flexibility in changing a design, such as legacy hardware that cannot be modified.
Thus, techniques are desirable for implementing DOCSIS 3.1 in to the cable infrastructure in an efficient manner, including implementing the parameters introduced in DOCSIS 3.1.